The present invention is related to identification of polymer compositions. More particularly, the present invention is related to non-destructive identification of polymer compositions via spectroscopic tags.
Automated identification of plastic compositions is desirable for a variety of applications, such as recycling, tracking a manufacturing source, anti-piracy protection, and the like. Historically, X-rays and infrared spectroscopy have been used to identify plastic materials. Tagging materials such as ultraviolet and near-infrared fluorescent dyes have also been used for the identification of plastic compositions.
In Cyr et al., U.S. Pat. No. 6,099,930, tagging materials are placed in materials such as digital compact discs. A near-infrared fluorophore is incorporated into the compact disc via coating, admixing, blending, or copolymerization. Fluorescence is detectable when the fluorophore is exposed to electromagnetic radiation having a wavelength ranging from 670 nanometers to 1100 nanometers.
Unfortunately, the use of fluorophores may be problematic under certain conditions. For instance, if multiple fluorophores are used, there may be an inaccuracy in the signals that are produced if the dye ages or leaches under normal use conditions, which can include, for example, exposure to ultraviolet light and high ambient temperatures. Additionally, additives used in the polymer can alter the ratio of fluoroescence intensities.
Due to the multitude of articles made by polymeric materials, there is a growing need to develop methods and tagging materials that a manufacturer can use to identify a product. Thus, methods and materials are constantly being sought which are effective, accurate, and easily detected.